1. Field of the Invention
The invention is based on a process for manufacturing an erosion-resistant turbine blade made of an (.alpha./.beta.)-titanium base alloy made by remelt alloying a tip of a blade section using a B-, C- and/or N- containing gas atmosphere with the aid of a high power energy source. A blade manufactured in accordance with such a process is preferably employed in low-pressure stages of steam turbines, since owing to its low density it meets, even if overall lengths are large, the specifications with respect to mechanical loadability at temperatures up to approximately 150.degree. C. In this temperature range the steam entering the turbine contains droplets which impinge at a high velocity on those faces of the turbine blade which are exposed to the incoming steam, in particular the leading edge of the blade and the blade surface sections adjoining the leading edge of the blade on the suction side. In the process,, the droplets may cause erosion damage. Particularly subject to wear and tear is the blade section situated in the region of the blade tip, since there the circumferential speed of the blade is largest.
2. Discussion of Background
A process of the type mentioned at the outset is described in EP-A-0 491 075. This process serves to produce a protective layer having high erosion resistance on a turbine blade made of an (.alpha./.beta.)-titanium base alloy in the region of the blade tip. In this case, the protective layer is generated by remelt alloying of the (.alpha./.beta.)-titanium base alloy at the surface in a boron-, carbon- or nitrogen-containing gas atmosphere by means of a laser. Such a layer has great hardness, compared with the untreated regions of the blade, and effectively protects the titanium base alloy situated underneath it against droplet erosion. It has been found, however, that a blade material protected against erosion in such a way has lower fatigue strength than the unprotected blade material.